DIAMOX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DIAMOX (DIAMOX).
Carbonic anhydrase inhibitor; decreases aqueous humor production by inhibiting carbonic anhydrase in ciliary processes, leading to reduced intraocular pressure. Also inhibits carbonic anhydrase in renal tubules, causing bicarbonate diuresis and metabolic acidosis.
| Metabolism | Metabolized primarily via hydrolysis to acetazolamide (active) and then further to inactive metabolites; minimal hepatic metabolism. |
| Excretion | Renal; 70-100% unchanged by tubular secretion and passive reabsorption; pH-dependent; alkaline urine increases elimination. |
| Half-life | 10-15 hours; prolonged to up to 24+ hours in renal impairment; clinical context: requires twice-daily dosing for continuous effect. |
| Protein binding | ~90% bound, primarily to carbonic anhydrase in erythrocytes and plasma proteins (albumin). |
| Volume of Distribution | 0.2 L/kg; distributes into total body water; concentrates in red blood cells, kidney, and eye. |
| Bioavailability | Oral: ~100% (well absorbed, but food may delay absorption). |
| Onset of Action | Oral: 1-2 hours; IV: 2-5 minutes; peak effect at 2-4 hours (oral). |
| Duration of Action | Oral: 8-12 hours (diuresis), 18-24 hours (ocular effects); IV: 4-6 hours (diuresis). |
| Molecular Weight | 222.25 |
| Action Class | Carbonic anhydrase inhibitor |
| Brand Substitutes | Acemax 250mg Tablet, Opt Tablet, ACTAMIDE 250MG TABLET, Zac 250mg Tablet, Actazid 250mg Tablet |
250 mg orally every 6-8 hours for glaucoma; 250-375 mg orally once daily for altitude sickness; 5 mg/kg IV or IM every 6 hours for edema in congestive heart failure
| Dosage form | TABLET |
| Renal impairment | GFR 10-50 mL/min: 250 mg every 12 hours; GFR <10 mL/min: avoid use |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use |
| Pediatric use | Glaucoma: 8-15 mg/kg/day orally divided every 6-8 hours; Edema: 5 mg/kg IV or IM every 6 hours |
| Geriatric use | Start at lowest dose (250 mg orally every 12 hours); monitor renal function and electrolytes due to increased risk of metabolic acidosis and hypokalemia |
| 1st trimester | Data limited; potential for teratogenic effects (e.g., limb defects) based on animal studies. Use only if benefit outweighs risk. |
| 2nd trimester | May cause fetal acidosis; avoid prolonged use. Fetal monitoring recommended. |
| 3rd trimester | Risk of kernicterus due to bilirubin displacement; avoid near term. May cause neonatal electrolyte disturbances. |
Clinical note
Comprehensive clinical and safety monograph for DIAMOX (DIAMOX).
| Placental transfer | Crosses placenta; detected in fetal plasma at concentrations similar to maternal levels. Significant transfer occurs. |
| Breastfeeding | Acetazolamide is excreted into breast milk in low concentrations. Infant exposure is minimal; however, monitor for possible metabolic acidosis or diuresis. Use caution in prematurity or neonatal illness. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to acetazolamide or sulfonamidesSevere hepatic disease (risk of hepatic encephalopathy)Severe renal insufficiency (e.g., anuria, GFR < 10 mL/min)Hyponatremia or hypokalemiaMetabolic acidosisAdrenal insufficiency (Addison's disease)
| Precautions | May cause metabolic acidosis; use caution in patients with pulmonary obstruction or emphysema., Sulfonamide derivative; may cause hypersensitivity reactions including Stevens-Johnson syndrome., Contraindicated in severe hepatic or renal dysfunction; may precipitate hepatic encephalopathy., Monitor serum electrolytes and blood counts during prolonged therapy., May impair mental alertness; caution when driving or operating machinery. |
| Food/Dietary | Avoid high-dose vitamin C (may increase risk of kidney stones). No other significant food interactions. |
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| Lactation Rating |
| L2 (Safer) |
| Teratogenic Risk | Diamox (acetazolamide) is a carbonic anhydrase inhibitor. Animal studies show teratogenic effects (limb malformations) at high doses, but human data limited. First trimester exposure may be associated with increased risk of congenital anomalies, particularly of the limbs and neural tube. Risk likely low but consider alternatives in first trimester. In second and third trimesters, no clear fetal toxicity but monitor for potential electrolyte imbalances and acidosis. |
| Fetal Monitoring | Monitor serum electrolytes (sodium, potassium, bicarbonate, chloride), renal function, and blood pH periodically. Assess for signs of acidosis or electrolyte imbalance. In pregnancy, monitor fetal growth and amniotic fluid volume if used chronically. For high-risk pregnancies, consider periodic fetal anatomy ultrasound if exposure in first trimester. |
| Fertility Effects | Acetazolamide has been associated with reversible decreases in sperm motility and count in some animal studies; human data limited. No known effect on female fertility. Discontinuation may reverse effects. |
| Clinical Pearls | DIAMOX (acetazolamide) is a carbonic anhydrase inhibitor used for glaucoma, altitude sickness, and edema. It can cause metabolic acidosis; monitor electrolytes. Avoid in severe hepatic or renal impairment. Use with caution in patients with sulfonamide allergy. |
| Patient Advice | Take exactly as prescribed; do not skip doses. · May cause drowsiness or dizziness; avoid driving until you know how it affects you. · Drink plenty of fluids to prevent kidney stones. · Avoid alcohol as it may increase side effects. · Report any signs of allergic reaction (rash, hives, difficulty breathing) immediately. |